Generally, the acquisition of optical image data for computer storage and/or facsimile transmission requires the use of complex optical sensors. Typically these have ranged from vacuum tube type photo-diodes, photo-transistor devices, charge-coupled devices, and the like. Generally, these sensors require an external light source capable of uniformly illuminating the image to be acquired. Because of this requirement, the physical size of these sensors is often large. In addition, they require a lens for optically focussing an image onto the photosensitive region of the sensor which adds to the complexity of the apparatus.
Several techniques are known for acquiring optical image data using a scanning procedure. One technique uses a horizontal array of optical sensors that view the medium containing the image while it is uniformly illuminated by a horizontally disposed light source. In this technique, the medium is moved vertically relative to the optical sensor array. Another technique uses a vertical array of optical sensors and a uniform, vertically disposed light source; and the array is moved horizontally across the image in one pass. Afterwards, the image is vertically displaced by an amount equal to the vertical height of the optical sensor array. Both of these techniques require special mechanical apparatus specifically designed to effect the required movement of the image bearing medium and the optical sensor.
While both of the above described techniques perform satisfactorily, the equipment required is relatively costly. It is an object of the present invention to provide a new and improved scanning technique based on relatively inexpensive optical sensors, and mechanical devices not specifically designed for image scanning purposes.